Maintaining a balance between energy production and energy demand has always been difficult, especially for large-scale energy production. For instance, traditional electric utilities operate large, efficient power generating plants configured to produce electricity at a rate sufficient to meet a base load. However, when demand rises, even traditional plants may fail to meet the high load. Improvements in energy capture and conversion using alternative energy sources have exacerbated issues with energy production/demand load balancing as alternative energy sources such as wind and solar also tend to be intermittent and unpredictable. The inability to adequately meet hourly, daily, and seasonal fluctuations in demand has slowed large scale penetration of clean, non-traditional energy sources such as wind and solar into the electric grid.
Energy storage systems that can efficiently store excess off-peak energy for use at peak-demand times would go a long way to increasing adoption of alternative energy technologies. Water-based energy storage systems have long been utilized to provide load balancing between energy production and demand. This method stores energy in the form of increased potential energy of water, pumped from a lower elevation to a higher elevation during times of low demand and excess energy production. Low-cost surplus off-peak power is typically used to run the pumps. During periods of high demand, the stored water is released through turbines to retrieve the stored energy and produce power. Unfortunately, losses of the pumping process makes water-based energy storage inefficient.
Compressed Air Energy Storage (CAES) is another example of an energy storage technology that shows promise for storing a large amount of energy at an economical cost. In this system, excess energy produced at low demand is used to compress air that is then stored in a suitable facility (e.g., underground storage). At high demand, the compressed air is expanded to drive a turbine and retrieve the stored energy in production of electricity. While there exist operational CAES systems, they suffer from low overall efficiency.
Accordingly, there is a need for improved energy storage systems. In particular, there is a need to efficiently store energy created by clean, alternative energy sources during times when power demand is low and/or production capability is high so that the energy might be supplied to consistently meet power demands even at times when production capability is low.